Controlling device for self-focusing electrical-arc lamps.



J. L. BOYLE.

'CONTROLLING DEVICE FOR SELF FOCUSING ELECTRIC ARC LAMPS.

APPLICATION FILED MAR. 31. 1916.

1,262,91 6. Patented Apr. 16, 1918.

3 SHEETS-SHEET 1.

@f A f 9 07- Mia? J. L. BOYLE.

CONTEOLLING DEVICE FOR SELF FOCUSING ELECTRIC ABC LAMPS.

`APPLICATION FILED MAR. 31.1916.

Patented Apr. 16, 1918.

3 SHEETS-SHEET 2.

L L. BOYLE.

CONTROLLING DEVICE FOR SELF FOCUSING ELECTRIC ARC LAMPS.

. APPLICATION FILED MAR. 31, 19H5. 1 ,262,91 6. Patented Apr. 16, 1918.

3 SHEETS-SHEET 3.

fili/eminr 'NTD STA PATNT OFFCE,

JQHN L. BQYLE, ,0F BOSTON, ]LSLISSACHUSETTS,-

CONTB'OLIJNG DEVICE FOR- SELF-FOCUSlNG ELEGTRC-ABC @Ml/@S Substitute.for applioetion` Serial No. eil, filed Januar-y 13, 1913'.

Specification of Letters Patent.

,Patented Apr. 16, 1.918.-

This application ledMarch 31, 1916.-

SerialNp. 87,904.

T his invention nelates to controlling :dee

vices for electric are lamps end is a substitute for application,Seri-al. #7411672., filed January 13, 19,13.

The -ohjeot of. the intention is to provide eontrollingfnieansforelectrie ,are lenip whereby the are shall be automatically main.- tainedet e predetermined point, euch .for example as `the optical :Center .ofo .lenswith which thelamp ie employed- Alfthough the invention isVyshown eonneetion with what is commonly termed va focusing arc lainp itwill be understood that it is also adapted for use with a non-focusingare lamp,

One forni of the invention contemplates the provision ofeleotrorresponsive means controlled by the ,current passi-n0r from oneto the other electrode for lowering or rais.- ihg the are eooordng as,lthe, .Center of the same. moves lup or down with respect to apredetermined point, eaused by` the koonsumption of theeleetrodes. Inearn-ying outthis form of the invention aV contact-member is provided.,which is adri-rated` tor malte contact with one `or .the other or bothof the electrodes adjacent `the are, and this oontaoi member is oorninonto two y circuits, eaoh .oi-r.- ouit containing an ,electro-responsivedevice arranged to control actuating-means by which the lamp is raisedand lowered, and the ero maintained et e phedetermihed point, one ofsaid circuits being ooroieeted to the upper electrode and the Vothercircuit being connected to the lower electrode.

The heet of the ordinary are ie lvery ntenee, ySo that it preierohle to.more the @ontw-member intermtt tlv into end ont of .Contact therewith orwith the electrodes et Short intervalsbnt es Said @omelet-memeher heey:rem-ein o oofinnonely in oonteot with the are., etleeet. fore Shortperiod .1o.f`vtme., I.

have, therefore Freeride@ .ineens for emotie ing innemen, feuitehle.,both oi these oomtions A further feature. of the ilwention .oon-

teniplates the provision of a posi/tive stop which is arranged to beinserted periodically between the electrodes, and then the electrodesare brought into engagement therewith to relocate the are.

l will describe Iny invention in the ollowing spekoifieation, and willrlpoli-nt out the novel features thereof the appended claims,

In the accompanying drawings,

Figure 1 is a diagrammatic view illus tre-.ting one embodiment of vtheinvention, suitable for use with an ordinaryaa-re.

Fig. 2 is a plan view of the mechanism for raising and lowering the are.

F ig.3 is a side elevation of the mechanism shown in F ig.v 2.

Fig. 4- is a Vplan view .of the mechanism for controllng the circuits ofthe raising and lowering mechanism.

Fig. 5 is a side elevation of the same.

Fig. 6 is aside elevation of the mechanism for actuating the .oontaotwhich engages the electrodes Figs. 7, 8 and 9 are details ofi the mecha;

nisrn for periodically closing the circuit` which eothotee the .ContactFLI- 10 :is a diagrammatic -rfiew ior 1e modified form of thei,evention- Fig. 1l is a diagrarnrnalti ViewV Qi an. other modified formof the invention.

Fig. 112 is a diagrarnrnatie view of still another ined-ined forni rofthe invention.

As illustrated in Figs. 1 .to 9, inelusiive, 10 represents housing foran electric are amp, Whioh mer be o f the Well-known focusing type,having an upper electrode 1 2 and a lower electrode 1 4. The lamp isdesigned to be arranged upon any suitable adiueteble .Support or table1.6.` so that vthe position .of the are 18, formed between theelectrodes 12 and 1 4. may be vertically ad: justed as -desi-red `withrespect `to -a predef. terroineel poiliit-y euch jthe, ootoel center? ofe 1ere, 01- the like The oleetrodes preereblv entre .long endmenne movberno: vided Yfor keeping them in perfeot Ye1inerme.1n-

Arreneed So to engage. .ei-ther or both ofthe eleotroflee 12. ieYa,.comoet--nlelnloer 20, which may be of carbon or other suitableytaining an electro-responsive device.

to be moved periodically into and out of engaging position by mechanismwhich will be hereinafter described. lVhen the arc is in its correctposition and the contact-memloer is moved into engaging position it mayengage the are only, but when the arc has shifted to a position above or.below the predetermined point, due to the consumption of theelectrodes, said contact-member will engage one or the other oi saidelectrodes according to which direction the arc has shifted.

The upper electrode 12 is connected by a wire 22 to coil 23 of anelectro-responsive device, such as a relay-switch, and said coil isconnected by wires 24, 25, to the contactmember 20. The lower electrode111 is connected by a wire 2S to coil 30, of an electroresponsivedevice, such as a relay-switch, and said coil is connected by a wire 31to the wire 25, which leads to the contactmember 20. Thus there are twocircuits having a common conductor connected to the contact-member 20,each circuit con- Said devices or relay-switches are adapted to controlmechanism for moving the lamp bodily up or down as required.

The mechanism here shown for raising and lowering the lamp comprises apair of electro-magnet coils 32, 34, arranged in a suitable housing 35which contains the sup- Jort or table 16. The coil 32 is connected by awire 36 to a stationary contact-member A87, and is connected by wires 88and 39 to a supply-wire 10. The coil 31 is connected by a. wire 42 tothe wire 39, and is connected by a wire 44: to a stationarycontact-meinber 45. A stationary contact-member 46, adjacent thecontact-member is connected'to the supply-wire 4S, and a stationarycontact-member '19, adjacent the contactmember 39 is connected by a wire50 to the said supply-wire 4S. The contact-members 45 and 46 are adaptedto be bridged by a switch-arm 52 carried by an armature 53 for the coil23, and the contact-members 37 and 49 are adapted t0 be bridged by aswitch-arm 5% carried by an armature 55 :tor the coil 30.

The electro-magnets 32, 31, are preferably solenoids having slidableiron cores or plungers 60, 61, respectively, arranged to pass throughguides 62. |The inner end of each core is connected to the corresponding end of a brass or other non-magnetic rod 64, slidable through aguide 66, and provided at its outer end with a cross-bar 68. The ends ofeach cross-bar are connected to retractile springs 69, 70, which areattached to adjusting-screws 72, 7 3, by means of which the tension ofsaid springs is adjusted.

-A lpawl 74 is pivotally connected to the outer end of the core and isheld in yielding engagement with a ratchet-wheel 7 6, by a spring 77;and a pawl 7S is pivotally connected to the outer end of the core 61 andheld in engagement with a ratchet-wheel 80 by a spring 81. The pawls 71and 'TS are normally out of engagement with the ratchet-wheels 76 and80, respectively, but are brought into engagement therewith by themovement of the cores 60 and 61, respectively, when their respectivecoils 32 and 31- are energized. The ratchet-wheels 76 and 80 are 'taston a vertical shait 82 journaled in a supporting-base 81, and providedat its upper end with a screw-threaded portion 86 which engages a nut 8Tsupported by brackets S8 depending from the under side of the table 16.A pair of sockets 90 are secured to the under side of the table 16 andreceive guide-rods 91 which project upward from the base 81:. lVlien thecoil is energized its core 60 is drawn in and the ratchet-wheel 7 6 isrotated clockwise thus turning` the screw 86 to raise the table 16, thecross-bar 63 is moved outward and the springs 69 and 70 are put undertension. When the coil 32 is denergized the core 60 and connected partsare returned to normal position, as shown in Fig. 2. lVhen the coil Silis energized the core 61 is drawn in and the ratchetswheel S0 is rotatedcounter-clockwise, thus turning the screw 86 to lower the table 16. Bythus raising or lowering the table 16 the are 18 is raised or loweredwith respect to the predetermined or focus point.

The electro-responsive devices for controlling the operation of theraising and lowering mechanism are shown diagrammatically in Fig. 1, butthey may be constructed asA shown in Figs. 41 and As here shown, thecoils 23 and 30 are solenoids having slidable iron cores or plungers100, 101, passing through guides 102, 103, and connected at their outerends to springs 104, 105. The inner ends of the cores 100, 101, areconnected to non-magnetic rods 108, 109, passing through guides 110,111, and provided at their outer ends with casings 112, 114. Each casinghouses a spring 115 which engages the opposing end of one of the rods10S, 109, and said springs also engage the inner ends of rods 116, 117,slidable in said casings. rlhe rods 116, 117 are provided with Contactblocks 11S, 120, suitably insulated therefrom and adapted to bridge thestationary contacts 45, 116 and 37, 19, re snectively. In thisc.,;istruction the contact blocks 118 and 120 are yicldingly supportedand are adapted to adjust themselves to malte a firm engagement with thestationarv contacts when the coils are energized. y

lVhen the coils 23 and 30 are energized their cores 100 and. 101'aredrawn in and the springs 104 and 105 are put under tension. In order toprevent a too rapid movement of the cores and connectedr parts whenreturning to normal position, a retardingdevice or escapexnent isprovided for each Core. It comprises a shaft 125 journaled in bearings126 and provided with blades or vanes128. A ratchet-vvheel 130 isailixed to the shaft 125 and is adapted to be engaged by a paivl 132carried by the core of the solenoid. When the .core is drawn back by itsspring. 104, or 105, the teeth of the pawl engage the correspondingratchetsvheel to rotate the shaft 125, and the comparatively largesurfaces of the vanes 128 produce a retarding action on said shaft.

The contact-member 2O is mounted upon a holder 140 which is yieldinglyand slidably connected to a rod 141 passing through a guide 142. Theinner end of the rod 141 is connected to the inner end of a magneticcore144 which is slidable Within a solenoid coil 146, and is connected atits outer end to a spring 148.

The coil 146 is periodically energized to bringl the contact-member 20into engage` nient with one or the ,other of the electrodes 12, 14. Toaccomplish this a continuously ruiming motor is provided, which may beof any Well-known r suitable construction, although an electric-motor150 is here shown, having its armature connected to Wires 151 and 152,leading to the supply-wires- The motor is provided with a shaft 154having a Worm 155, which engages a Wor-m-wheel 1.56 on a shaft 1.57, andthe llatter is provided with a Worm 158, Ywhich engages a Worm Wheel'159 on a shaft 160. Aliixed to the shaft .160. is a drum 162, made ofinsulating material, preferably Wood.. Mounted on the periphery of thedrum 162 is a contact-plate 164 havingv an overhanging upper edge .andthis plate is covered over a considerable portion of its area by aninsulating plate 166, also having its upper edge overhangin. A pair ofspringv contact-arms 116,8, 169 are adapted to :engage the peripheryo1"- the drum 162 and to Vslide up over the plates 166 and 164. As thearms 168, 169 move past the upper edge of the insulating plate 166 theyare snapped quickly against the contact-plate 164, see Figs. 8 and 9, tomake a good contact therewith and establish the circuit, and then asthey move past the upper edge of the plate 164 they are snapped quicklyagainst the periphery ot the drum to break the circuit. The arm 168 isconnected by a Wire 1Z0 to one end of the coil 146, the other end ofAsaid coil being connected by a Wire 172 to the return-wire 48, of' thesupplyy circuit, and thek arm 169 is connected by a wire 174 to the'supplywvire 'The drivingmechanism for the drum- 162 is preferably soAtimed that-the lcircuit through the coil 146 is momentarily closedevery three minutes or thereabouts.

The operation of this form of the invention is as follows Normally thecurrent passes from the electrode 12 across the arc 18 to the electrode14, said electrodes being connected in circuit in a well-known manner.The current divides in the .electrode 12, some passingthrough the wire22, .Coil 23, Wires 24, 3.1 coil 30 and Wire 28 to the electrode 14. 1twill be noted that the coils and 8O are in series, and they are soconstructed that comparatively little current passes through them, notenough to attract their armatures.

l/V hen the plate 164 closes the circuit through the coil 146, said coilis energized and moves the contact-member into engaging position. Tf thecenter of 'they arc 18 is in its correct position the contact 20 willengage both electrodes and there will be no eect on the coils and tomove their armatures. Suppose, however, that the arc is below therequired point, then the contact-member 2O Will engage the upper electrode 12 and thus short-circuit the coil This enables a larger portionor' the currentto pass through the coil 8O to energize it sutllicientlyto attract its armature and bridge the contact-members 37 and Thiscloses the circuit through the coil 32, Which thus becomes energized anddrawn in its core 60. The pand 74 engages the ratchet-Wheel 76 andimpart-s a partial rotation to said ratchet-Wheel and to the screw 86 toraise the table 16 and with it the lamp. The circuit through the coil146 is then broken when the arms 168 and 169 leave the plate 164, andthe spring 148 retracts the contact-nehmer 26, Tr the arc is too highwhen the contact-member 20 is moved into engaging position the latterengages the lower electrode 14 and the coil 30 is short circuited. Thisallows the coil v28 to be energized sufficiently to attract its armature53 and bridge the contact-meinbers aid 46, thereby closing` the circuitthrough the coil 34 which operates the mechanism in the housing so tolower the lamp and are.

Contact 2() is adapted to be periodically moved into contact With thearc or its electrodes at some predetermined rate, say about once inthree minutes. il" it touches one .of the electrodes the lamp isadjusted away from the contact until equal current flows in both relays,and then the lamp control ceases to act. The arc can new be displacedfrom the predetermined `lined point at which contact `2O is located byan amount equal to the difference in unequal carbon consumption duringthe period between adjustments. This Shifting of the arc is, inpractice, so smallE as not t0 affect the practical operation of theapparatus.

1n Fig. 10 I have shown a modified form of apparatus, in which thecontact-member which engages the arc is lrept in continuous Contacttherewith.

As here shown 200 represents a housing for the are lamp having an upperelectrode 202 and a lower electrode 20-1, said lamp being mounted on anadjustable table or support 16, as explained above, and said electrodesbeing connected in circuit in any well-known manner.

A xed contact-member 206 is mounted in a holder 207 which projects laterlly from a stationary support 208 suitably secured in place, and thiscontact-member is adapted to engage the arc 209, the engaging end ofsaid contact-member being located at the center of resistance the arc,when the mathematical center of the arc is in line with the opticalcenter of the lens.

The upper electrode 202 is connected by a wire 210 to one end ot' a coil211 oit' an electromagnet, and the other end of said coil is connectedby wires 212 and 214C to the contact-holder 207 which is connected tethe contact-member 206. The lower electrode 2041 is connected by a wire216 to one end or a coil 217, and the other end oi this coil isconnected by a wire 218 with the wire 2141.A

Thus there are two circuits having a common conductor 2111 connected tothe contactmember 20G, each circuit having an electroinagnet adapted tocontrol the mechanism lor moving the electrodes of the lamp insubstantially the same manner as explained in the foregoing.

The mechanism for raising and lowering the lamp comprises a pair ofelectromagnet coils 32 and 34 arranged in a suitabl housing 35 andconnected with mechanism which raises and lowers the table 16, asheretofore explained.

One end of the coil 32 is connected by a wire 220 with a stationarycontact-member 221, and the other end of this coil is connected by wires222 and 223 to a supplywire 224-. One end of the coil is con- Y nectedby a wire 226 with a stationary contact-member 228, and the ot1 er endet the coil is connected by a wire 229 to the wire.

223. A pair of stationary contact-ineinbers 230 and 231 are connected bywires and 235, respectively, to the supply-wire A double-throw switchblade is mounted on an arm 238 fulcrumed at 239 and provided with anarmature 2e/10 for the electromagnets 211 and 217. The operation of thisform of the invention is as follows Normally the greater portion of thecurrent passes from the electrode 202 across the arc 209 to theelectrode 204C, said electrodes being connected in circuit in arwell-known manner, and a small portion of the current passes through thewire 210, coil 211, wires 212, 214, holder 207, contact-member 206 toelectrode 20-1, and also wire 218, coil 217, and wire 210 to electrode201. The current in the coils 211 and 217 is balanced so that the arm238 remains in a central position when the center oi the arc coincideswith the conta t-member 20G.

Suppose, however, that the arc center is below the center olf thecontact-member 206, then the portion ot the arc extending between thecontact-member 20G and the upper electrode 202 is shorter than theportion of the are extending between the contact-member 200 and thelower electrode 201. Consequently, the resistance oil that portion ot'the arc between the electrode 202 and the contact-member 200 is lessthan that between the contactcneniber 200 and the el cctrode 204. Alarger current will therefore flow from the electrode 202 through thecontact-member 200, holder 207, wires 2111, 218, coil 217 and wire 210to electrode 204. The coil 217 thus becomes energized suf iiciently toattract the armature 210 and move the switch-contact 230 to bridge thestationary contact-members 221 and 231, thereby closing the circuitthrough the coil which actua-.tes the mechanism for lifting the lamp. 1fthe arc center should be above the predetermined point, the currentwould energize the coil 211 sul'licicntly to attract armature 2&0 andclose the circuit lnrough the coil 31 which actuates the lowingmechanisi'n. 1n Fig. 11 I have shown an auxiliary souixe'o current suchas a storage battery 40, which is connected by a wire 341 to the jperelectrode 12, and by a wire 342 to a coil 3414- ot' arelay-switch, saidcoil being connected by a wire 346 to a contact 348. The coil 344 isprovided with an armature 350 on a switch-arm 352 which is adapted tobridge contacli-members 35i, 355 connected in a controlling-circuit asexplained above. 1n this ligure circuit connections are shown for oneelectrode only, for simplicity, but, in practice, the controllingrcircuit connected between electrode 14E and contact 3118 con- 'tains aregulating relay with its operating attery in all respects similar tothe relay 344i and battery 340, as shown. The operation of this form ofthe invention is substantially as heretofore described. Then the arcbecomes displaced and contact 348 comes into contact with say electrode12, current from battery 340 flows between electrode 12, contact 348 andconnecting wires to regulating relay 344, which energizes apparatuspreviously described to restore the are to its normal position. Vhen theare becomes displaced in the opposite direction, and contact comes intoengagement with electrode 14, current flows through theother regulatingcircuit with its battery corretua-aaai@ spending to battery 340 andregulating relay corespondin to relay 344, and which circuit is notshown in the drawing, to adjust the arc to its normal position. ln thisiorm of the invention the arc current is not utilized to operate theregulating relays, but a separate source oi' current, viz, batteries340, are utilized for this purpose.

1n Fig. 12 l have shown another modiiied form ot' the invention, whichcomprises a housingV 400 for the arc lamp having an upper electrodee402anda lower electrode 404, said lampbeingmounted on an adjustable support406, vas explained above, and said electrodes being connected in circuitin any well-known manner.

f Theelectrodes 402, 404 are connected by a shunt, composed oi twobranches 407, 40S having balanced resistances 410, 411 connectedtherein. A lined contact-member 412 is mounted in a suitable holder andis adapted to engage the electrodes when the arc has moved from itscorrect position, as eX- plained above. The contact-member 412 isconnected by a wire 414 to the armature of a reversing-motor 416, saidarmature being also connected by a wire 418 to the junction of thebranches 407, 408 of the shunt.

The motor 416 is provided with a shaft 420 having a worm 421 whichmeshes with a worm-wheel 422 on a vertical shaft 424, said shaft beingscrew-threaded at its upper end to cooperate with a correspondinglythreaded bracket 426 secured to the adjustable support 406.

r1`he operation of this form of 'the invention is as follows l/Vhen thearc is in its correct position, a portion orn the current iiows throughshunt, but not. sufficient to operate the motor 416. 1f the are israised above the predetermined point, the lower electrode 404 willengage the contact-member 412, and the resistance 411 will beshort-circuited. Thereupon an increased current will flow through theshunt-branch 40?1 having the resistance 410, wire 418, armature of motor416, wire 414, and contact-member 412 to the electrode 404, and themotor 416 will be driven in the direction to cause the screw 424 tolower the support 406, and with it the lamp 400. 1f the arc becomeslowered below the predetermined point or optical center, the upperelectrode 402 will engage the contact-member 412, and the resistance 410will be shortcircuited. Thereupon an increased current will flow throughthe shunt-branch 406 having the resistance 411. This current will Howfrom the electrode 402 through the contact-member 412, wire 414,armature of motor 416, wire 418 and branch 408 to electrode 404, saidcurrent being in the opposite direction from that just set i'orth above,and consequently the motor is driven in the opposite direction to raisethe lamp'. The motor 416 maybe employed as an actuatingmeans `whencontrolled by the other forms or' controlling-means, which are shown inthe other iigures as well as when controlled by the means shown in TEig.12.

will be understood that, the electrodes in all the various forms of theinvention may, it desired, be inclosed from the atmosphere, thusincreasing their life.

1 claim:

1. Tie combination with the electricV are lamp having electrodes, ofmeans for varying the position of said are lamp, and means adaited to bebrought into contact with the electrodes thereof at a predetermined arcfor i' ment of said are lamp, substantially as decribed.

2. rlhe combination with an electric arc lamp having a pair ofelectrodes, of means of adjusting sL idk electrodes, and means adap tedto be brought into electrical contact with the electrodes at apredetermined arc forming place to determine said arc forming place,substantially a described.

3. rlhe combination with an electric arc lamp, of means for varying theposition of the lamp to correspondingly vary the position of the are,with respect to a predetermined tired point, and means adapted to bebrought into Contact with the are for controlling the direction ofmovement of said lamp, ubstantially as described.

4. an electric rc lamp including a table, a screw 'for raising andlowering the table, a pair ot' electrodes mounted on the table, a pairor" electromagnets, means operated by said magnets for turning saidscrew in opposite directions to adjust the elevation of the table, tocorrespondingly adjust the position or" the are between the electrodeswith respect to a lined point, and means affected by a change in theposition of the arc to control the direction of movement of said table.

5. The combination with an electric arc lamp, of means for varying theposition of the lamp, a pair of normally inoperative electro-responsivedevices, controlling actuation of said means, and means -forshortcircuiting one of said devices when the center of the are has movedaway from a predetermined point, substantially as described.

6. rEhe combination with an electric arc lamp, of means for varying theposition of the lamp, a pair of normally inoperative electro-responsivedevices controlling actuation of said means, and arranged to be operatedby a portion of the current passing through the lamp, and means forshort-circniting one of said devices when the center of the are hasmoved beyond a predetermined point, whereby the other of said deng jlacefor controlling the movevices is actuated to operate the arc-varyingmeans, substantially as described.

7. The combination with an electric are lamp, comprising a pair ofelectrodes, of electro-responsive means for raising and lowering thelamp, a contact-member arranged to engage said electrodes, and meansconnected to said contact-member arranged to control the operation ofsaid raising and lowering means, substantially as described.

8. The combination with an electric arc lamp, comprising a pair ofelectrodes, of electro-responsive means for raising and lowering thelamp, a contact-member, means for periodically moving said contactmember into and out 0f the arc space, and means connected to saidcontact-member for controlling the operation of said raising andlowering means, substantially as described.

9. The combination with an electric arc lamp, comprising a pair ofelectrodes, of a contact-member adapted to be brought into engagementwith said electrodes, means for intermittentlymovingsaid contact-memberinto engaging position, and means for raising and lowering said lampaccording as the center of the arc is below or above a predeterminedpoint, substantially as described.

10. The combination with an electric arc lamp, comprising a pair ofelectrodes, of

means for centering the arc, a contact-member adapted to electricallyengage the are at a predeterlnined point, a pair of opposedelectro-responsive devices arranged to control the operation of saidcentering means, said means being inactive when the center of the arc isat said predetermined point but adapted to be actuated by an unbalancingof the current flowing through said devices due to the movement of thecenter of the arc away from said predetermined point, substantially asdescribed.

11. A self-focusing electric arc lamp, comprising means for varying theheight or" the arc, a. motor, a contact-device actuated by said motor, acircuit arranged to be momentarily closed by said contact-device, meanscontrolled by said circuit for engaging the electrodes of said lamp, andmeans controlled by the current ot' the arc circuit for actuating themeans for varying the height thereof when its center has been moved awayfrom a predetermined point by an unequal consumption of the electrodes,substantially as described.

In testimony whereof, I have signed my name to this specification, inthe presence of two subscribing witnesses.

JOHN L. BOYLE.

Witnesses H. B. DAVIS, B. J. NoYEs.

Copies o! this patent may be obtained for ve cents each, by addressingthe Commissioner of Patenti.

Washington, D. C.

